1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine of a vehicle such as a passenger car, a truck or the like.
2. Description of Related Art
A slant nose type vehicle has recently been required to decrease a running resistance in the vehicle and to improve a field of vision for a driver. Further, a wide accommodation space of a vehicle compartment has recently been required to give better comfort to occupants of the vehicle. These requirements narrow an engine room space. In the engine room, an internal combustion engine, an alternator driven by the engine, and the like are disposed.
Further, an engine speed has been reduced to improve fuel economy, so that number of revolutions in an alternator has been reduced. In contrast, the number of current consumers such as a safety control device and the like has been increased, so that the alternator has been required to increase its generated electrical energy. Therefore, the alternator having a smaller size and a higher output is required. In this alternator, combustion heat per unit volume is heightened, and cooling performance is inevitably lowered.
In an alternator for a vehicle, a columnar rotor is disposed in a cylindrical stator, a pulley is disposed on a driving side of the rotor to receive a rotational force from an engine, and the rotor is rotated on its axis in response to the rotational force. In response to the rotation of the rotor and a field current supplied to the rotor, an alternating current is generated in a stator wiring of the stator. A generator voltage regulator adjusts a voltage of this current by regulating the field current. A rectifier rectifies the alternating current. The rectified current set at the adjusted voltage is output to electric consumers and a battery of the vehicle. Electronic devices such as the regulator and rectifier are disposed on an anti-driving side of the rotor opposite to the driving side. That is, the pulley and the group of electronic devices are disposed away from each other with the rotor between.
Because the current is generated in the stator wiring, this wiring acts as a heat generating member. However, because the cooling performance of the alternator has recently been lowered, constitutional members of the alternator are inevitably heated by the stator wiring at high temperatures. Therefore, there is a probability that the members be heated so as to exceed those allowable temperatures and be broken.
To prevent the members from being excessively heated by the stator wiring, Published Japanese Patent First Publication No. H11-155270 has disclosed an alternator wherein a space factor indicating a space ratio of the stator wiring to an allowable space for the wiring is heightened to reduce electric resistance of the wiring to a half level. However, the rectifier is generally made of diodes connected with one another in a diode bridge, so that the rectifier also acts as a heat generating member. Therefore, a problem based on heat generated by the rectifier is not solved in this Publication.
In recent years, the alternator has been required to further increase its output power. Therefore, the rectifier and regulator disposed on the anti-driving side of the rotor are easily heated so as to exceed those allowable temperatures, and the rectifier and regulator are sometimes broken. Particularly, the regulator is an electronic circuit member for controlling the generated current of the alternator. Therefore, even though the regulator does not break easily, malfunctions can easily occur in the regulator. In this case, the battery is excessively charged so as to shorten the life of the battery. To prevent the malfunction of the regulator, a heat dissipating fin attached to the regulator has been modified to improve heat dissipation of the regulator. However, heat cannot be sufficiently dissipated from the regulator.
Further, in another publication, a temperature sensor is attached to a regulator. When the sensor detects that the regulator is heated at a predetermined temperature, the alternator stops generating an electrical energy. However, a manufacturing cost of the alternator is heightened due to the sensor and a control system for stopping the energy generation. Further, it is difficult to reliably operate the sensor. In addition, when the operation of the alternator is stopped often, the battery cannot be sufficiently charged.
Moreover, high temperature members such as an exhaust manifold of an engine are often disposed on a rear side of an alternator (i.e., anti-driving side of rotor) so as to be close to a regulator. In this case, the regulator is further heated.
Furthermore, Published Japanese Patent First Publication No. H05-199707 has disclosed an alternator wherein both a regulator and a rectifier are disposed on a front side of an alternator (i.e., driving side of rotor). However, the regulator still receives heat from the rectifier, and the heat cannot be sufficiently dissipated from the regulator.